Electromagnetic radiating horn utilizing aperture loading



y 3, 1958 w. w. HENDERSON 2,834,960

ELECTROMAGNETIC RADIATING HORN UTILIZING APER-TURE LOADING Filed Feb. 28. 1955 3 Sheets-Sheet 1 May 13, 1958 w. w. HENDERSON 2,834,960

ELECTROMAGNETIC RADIATING HORN UTILIZING APER-TURE LOADING Filed Feb. 28. 1955 I s Sheets-Sheet 2 Filed Feb. 28, 1955 y 1958 w. w. HENDERSON 2,834,960

ELECTROMAGNETIC RADIATING HORN UTILIZING APERTURE LOADING 3 Sheets-Sheet 3 ELECTROMAGNETIC RADIATING HORN UTILIZING APERTURE LOADING William W. Henderson, Old Greenwich, Conn., assignor, by mesne assignments, to the United States of America as represented by the Secretary of the Navy Application February 28, 1955, Serial No. 491,235

3 Claims. (Cl. 343-786) This invention is concerned with radiated electromagnetic waves having wave lengths in the very short wave length region.

The use of horns which are essentially'wave guides having flared ends for the radiation of short wave lengths electromagnetic waves rather than antennae arrays has become more common for it has been found that the dimensions of such horns are advantageous at the higher frequencies. The problems encountered in such horns are those of providing high gain, control of impedance and radiation pattern characteristics and obtaining horns Suitable for broad band radiation.

It is an object therefore of this invention to provide an electromagnetic wave radiating horn which is capable of a high degree of directivity when radiating polarized waves.

Another object of this invention is the provision of a simple radiator which is capable of operating over a wide band of frequencies.

A further object of this invention is the provision of a radiating horn having obstacles in its aperture to improve the impedance transformation characteristics and to permit the horn to operate without attenuation at frequencies below cutoff for the equivalent rectangular wave guide.

A still further object of this invention is the provision of tapered metal obstacles with rounded ends in the aperture of a radiating horn to improve the impedance, transmission and radiation pattern characteristics of the horn.

Other objects and many of the attendant advantages of this invention Will be readily appreciated as the same becomes hetter understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Figure l is a side view of one form the radiating horn may take.

Figure 2 is a plan view of the horn of Figure 1.

Figure 3 is an end view of the horn of Figure 1 along the line 3-3.

Figure 4 is a side view of another embodiment of the horn.

Figure 5 is a plan view of the horn of Figure 4.

Figure 6 is a sectional view along the line 6-6 of Figure 5.

Figure 7 is a side view of a third embodiment of the radiating horn.

Figure 8 is a plan view of the horn of Figure 8.

Figure 1 shows one form a horn embodying the invention may take. The horn 1 is provided with a wave guide portion 12 and the flared portion 3 which enhances the radiation capabilities of the wave guide by giving better directivity and higher gain. A coaxial line to wave guide transformer 4 is mounted in the wave guide and coupled to the coaxial line 5.

Constantly increasing space 6 is provided by the flared portion 3 for the propagation of the electromagnetic waves. Mounted in the space 6 are a pair of elongated metallic obstacles 7. Each of these obstacles is tapered Cit in a first plane normal to the longitudinal axis of the obstacle as shown by the sides, or walls 8, 8 of eachobstacle. The obstacles are "also tapered in a second plane normal to the first plane of taperas shown by the sides or walls 9. The obstacles on their upper and lower surfaces respectively contact upper and lower interior surfaces of the flaredportion of the horn. One end 10' of each obstacle projects beyond the open end or aperture of the horn and is rounded in one plane.

The rounded ends 10 of each obstacle improve the impedance match of the radiating horn with the free space. The obstacles themselves permit operation of the hornat frequencies below that of cutoff for the dominant mode for the, equivalent rectangular waveguide. The tapered construction of the obstacles provides better matching of the feed point impedance with aperture impedance. q

It has been found also that a horn constructed as described herein insures broader horizontal plane coverage and in wide band operation the horizontal plane pattern coverage varies from the low frequency end to the high frequency end by a factor of some which is a considerably smaller beam width change than is the case when simple slot apertures are employed. Further, the use of these obstacles which divide the E-plane into a ladder structure permits better utilization of the horns vertical dimensions to obtain smaller vertical plane beam widths.

The form of the horn shown in Figure 1 is suitable for operation over the band of 1000 to 2600 me. The horn may take other forms as described below for operation over other frequency bands.

A horn suitable for operation over the frequency band of 4150 to 7350 me. is shown in Figures 4 to 6.

The reference numeral 12 generally designates the horn. The throat or wave guide portion 13 of the horn provides the feed point While the tapered portion 14 provides the radiating element of the horn. Coupled on the horn by means of the coaxial line to wave guide transformer 15 is the transmission line 16. Mounted in the space 17, wherein the electromagnetic waves are propagated, are the obstacles 18 held in position by the pins or other suitable support means 19 passing through the sides of the horn. The obstacles 18 are provided with upper and lower tapered surfaces 20 and with tapered sides 21.

Each obstacle also has a rounded end 22 projecting beyond the apertured end of the horn and the upper and lower edges 23 of the horn are also rounded.

Figures 7 and 8 show an embodiment of the invention suitable for operation over the frequency band of 7,050 to 10,750 me. The horn 30 is provided with a wave guide end 31 and a tapered enlargement 32. The transmission line 34 is coupled to wave guide or feed point 31 by means of the transformer 33. Mounted in the space 35 are a pair of metallic obstacles 36 held in position by the pins 37 passing through the sides of the horn. The obstacles are provided with tapered upper and lower surfaces 38 and with rounded ends 39 projecting beyond the free end of the horn. Rounded projections 40 are also provided on the upper and lower sides of the horn.

Thus, in accordance with the above teachings, it is possible to construct wide band source or receiving antennae with good impedance properties whose H-plane patterns can be made large and more consistant than for ordinary horns with comparable or larger physical dimensions and whose E-plane patterns can be controlled.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. it is therefore to be understood that within Patented May 13, 1958 the scope of the appended practiced otherwise than as specifically described.

What is claimed is: i

1. An electromagnetic; wave radiating. device comprise ing aflared horn, having a. throatsectionat one end, theref. and, four. outwardly flar d Walls, exten ing; from said throatrsection, definingan .cnlargedg'aperture. at. the, 01?- posite; end ther of an n ir-ot ppqsed elongated; members disnosed' within, said new and: extendingf c tween, said throat section and, said; enlarged. apenturewith' oneof the. extremities of said pairof opposed elongated members terminating a, predetermined distance, beyond the plane, of, said, enlarged, aperture; andv the opposite exclaims the invention may be tremities, of said. pair (ii-opposed elongated members,-

terminating proximate, said throat section, the extremities of said. pair oi opposedelongated, members terminating a. predetermined distance, beyond said, plane. oi 'said enlarged aperturev being rounded and eecllof said opposed. elongated members being'rectangnlar incross-section, over substantially its entire length, each of said opposedelongated, members being bound by. tapered, walls and, pro gressively increasing, in, cross-section. from; a, point in the plane of said enlarged aperture to the extremity thereof terminating proximate said throat section.

2. An electromagnetic wave radiating device as claimed in claim 1 wherein said pair of opposed elongated members is disposed within said flared horn whereby one tapered wall of each of said opposed elongated members engages a flared wall of said horn.

3. An electromagnetic wave radiating' device as claimed in claim 1 whereinsaid pair of opposed elongated members are spaced, firom; the flared wallsiof said horn.

Refierences Citedtin the file of this. patent Hill Bool Co.,,Inc., New York; pagesv 359-361 relied on. 

